U.S. patent application number 12/126230 was filed with the patent office on 2008-11-27 for electrode assembly and secondary battery using the same.
This patent application is currently assigned to Samsung SDI Co., Ltd.. Invention is credited to Hyorim BAK, Youngchurl Chang.
Application Number | 20080292966 12/126230 |
Document ID | / |
Family ID | 39816665 |
Filed Date | 2008-11-27 |
United States Patent
Application |
20080292966 |
Kind Code |
A1 |
BAK; Hyorim ; et
al. |
November 27, 2008 |
ELECTRODE ASSEMBLY AND SECONDARY BATTERY USING THE SAME
Abstract
An electrode assembly and a secondary battery including the
same. The electrode assembly includes: a positive electrode plate
including a positive electrode active material applied to a
positive electrode collector; a negative electrode plate including
a negative electrode active material applied to a negative
electrode collector; a separator disposed between the positive
electrode plate and the negative electrode plate; and a ceramic
layer disposed on a portion of the positive or negative electrode
plate, adjacent to an outer surface of the electrode assembly. The
positive electrode plate, the negative electrode plate, ceramic
layer, and the separator are wound together. The ceramic layer
prevents a short-circuit between the positive electrode plate and
the negative electrode plate, and extends along between about 40%
and 90% of the length of the positive or negative electrode plate,
from a winding end thereof.
Inventors: |
BAK; Hyorim; (Yongin-si,
KR) ; Chang; Youngchurl; (Yongin-si, KR) |
Correspondence
Address: |
STEIN, MCEWEN & BUI, LLP
1400 EYE STREET, NW, SUITE 300
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung SDI Co., Ltd.
Suwon-si
KR
|
Family ID: |
39816665 |
Appl. No.: |
12/126230 |
Filed: |
May 23, 2008 |
Current U.S.
Class: |
429/246 |
Current CPC
Class: |
H01M 50/431 20210101;
H01M 10/0431 20130101; Y02E 60/10 20130101; H01M 4/366
20130101 |
Class at
Publication: |
429/246 |
International
Class: |
H01M 2/14 20060101
H01M002/14; H01M 4/00 20060101 H01M004/00; H01M 10/02 20060101
H01M010/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2007 |
KR |
2007-51094 |
Claims
1. An electrode assembly of a secondary battery comprising: a
positive electrode plate comprising a positive electrode active
material applied to a positive electrode collector; a negative
electrode plate comprising a negative electrode active material
applied to a negative electrode collector; a separator disposed
between the positive electrode plate and the negative electrode
plate; and a ceramic layer to prevent the short-circuit between the
positive electrode plate and the negative electrode plate, disposed
along the positive electrode plate, and extending from a winding
end of the positive electrode plate, along between about 40% and
about 90% of the length of the positive electrode plate, wherein
the winding end is located at an outer ring of the electrode
assembly, and the positive electrode plate, the negative electrode
plate, the ceramic layer, and the separator are wound together.
2. The electrode assembly as claimed in claim 1, wherein the
ceramic layer extends along less than about 70% of the length of
the positive electrode plate, from the winding end, which is
located at the outer ring of the electrode assembly.
3. The electrode assembly as claimed in claim 1, wherein the
ceramic layer extends along between about 45% and about 70% of the
length of the positive electrode plate, from the winding end.
4. The electrode assembly as claimed in claim 1, wherein the
separator comprises a polymer resin film, and the ceramic layer is
formed on at least one surface of the film.
5. The electrode assembly as claimed in claim 1, wherein the
ceramic layer is formed on at least one surface of the negative
electrode plate.
6. The electrode assembly as claimed in claim 5, wherein the
ceramic layer is formed on a layer of the negative electrode active
material.
7. The electrode assembly as claimed in claim 5, wherein the
negative electrode plate includes a non-coating portion where the
negative electrode active material is not applied and the ceramic
layer extends onto the non-coating portion.
8. The electrode assembly as claimed in claim 1, wherein the
ceramic layer is formed on at least one surface of the positive
electrode plate.
9. The electrode assembly as claimed in claim 8, wherein the
positive electrode plate includes a non-coating portion where the
positive electrode active material is not applied, and the ceramic
layer extends onto the non-coating portion.
10. The electrode assembly as claimed in claim 8, wherein the
ceramic layer is formed on a layer of the positive electrode active
material.
11. The electrode assembly as claimed in claim 1, wherein the
negative electrode plate is wound around the positive electrode
plate, and the ceramic layer is formed on a surface of the negative
electrode plate, which faces the positive electrode plate.
12. The electrode assembly as claimed in claim 1, wherein the
positive electrode plate is wound around the negative electrode
plate, and the ceramic layer is formed on a surface of the negative
electrode plate that faces the positive electrode plate.
13. An electrode assembly of a secondary battery comprising: a
positive electrode plate comprising a positive electrode active
material applied to a positive electrode collector; a negative
electrode plate comprising a negative electrode active material
applied to a negative electrode collector; and a separator being
disposed between the positive electrode plate and the negative
electrode plate, the electrode assembly comprises a ceramic layer
to prevent the short-circuit between the positive electrode plate
and the negative electrode plate, disposed along the negative
electrode plate, and extending from a winding end of the negative
electrode plate, along between about 40% and about 90% of the
length of the negative electrode plate, the winding end being
located in an outer ring of the electrode assembly, wherein the
positive electrode plate, the negative electrode plate, and the
separator are wound together.
14. The electrode assembly as claimed in claim 13, wherein the
ceramic layer extends along less than about 70% of the length of
the negative electrode plate, from the winding end.
15. The electrode assembly as claimed in claim 13, wherein the
ceramic layer extends along between about 45% and about 70% of the
length of the negative electrode plate, from the winding end.
16. A secondary battery comprising: a can having an opening; an
electrode assembly comprising, a positive electrode plate
comprising a positive electrode active material applied to a
positive electrode collector, a negative electrode plate comprising
a negative electrode active material applied to a negative
electrode collector, a separator disposed between the positive
electrode plate and the negative electrode plate, and a ceramic
layer to prevent a short-circuit between the positive electrode
plate and the negative electrode plate, disposed along the positive
electrode plate, and extending from a winding end of the positive
electrode plate, along between about 40% and about 90% of the
length of the positive electrode plate; and a cap assembly
comprising, a cap plate to seal the opening of the can, and an
electrode terminal being coupled with the cap plate in an insulated
state, and electrically connected to the electrode assembly,
wherein the winding end is located at an outer ring of the
electrode assembly, and the positive electrode plate, the negative
electrode plate, the ceramic layer, and the separator are wound
together.
17. A secondary battery comprising: a can having an opening; an
electrode assembly comprising, a positive electrode plate
comprising a positive electrode active material applied to a
positive electrode collector, a negative electrode plate comprising
a negative electrode active material applied to a negative
electrode collector, a separator disposed between the positive
electrode plate and the negative electrode plate, and a ceramic
layer to prevent the short-circuit between the positive electrode
plate and the negative electrode plate, disposed upon the negative
electrode plate, and extending from a winding end of the negative
electrode plate, along between about 40% and about 90% of the
length of the negative electrode plate; and a cap assembly
comprising, a cap plate to seal the opening of the can, and an
electrode terminal being coupled with the cap plate in an insulated
state, and electrically connected to the electrode assembly,
wherein the winding end is located at an outer ring of the
electrode assembly, and the negative electrode plate, the negative
electrode plate, the ceramic layer, and the separator are wound
together.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Application
No. 2007-51094 filed May 25, 2007, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Aspects of the present invention relate to an electrode
assembly and a secondary battery using the same, and more
particularly, to an electrode assembly that includes a ceramic
layer disposed adjacent to an outer surface of the electrode
assembly, and a secondary battery using the same.
[0004] 2. Description of the Related Art
[0005] Generally, a lithium secondary battery can be rechargeable,
and thus, repeatedly usable, which is different from a primary
battery, which cannot be recharged. Secondary batteries are widely
used as main power sources in high-technology electronic devices,
such as, a personal digital assistant (PDA), a notebook computer,
and the like. Currently, interest in secondary batteries is
increasing and the development of secondary batteries is also being
rapidly performed. This is because secondary batteries are
generally lightweight, have high energy densities, high output
voltages, low discharge rates, and long lifespans.
[0006] Secondary batteries are classified into nickel-metal hydride
(Ni-MH) batteries, lithium ion (Li-ion) batteries, and the like,
based on electrode active materials used therein. The lithium ion
(Li-ion) batteries may be classified based on the type of
electrolyte, for example, a liquid electrolyte, a solid
electrolyte, or a gel-type electrolyte. Also, the secondary
batteries are classified into various types, such as, a can type, a
pouch type, and the like, based on the shape of a can within which
the electrode assembly is disposed.
[0007] A lithium ion (Li-ion) battery has an operational voltage of
about 3.6V, and is three times more compact than a Ni--Cd battery,
or a Ni-MH battery. Also, since the weight-to-energy density of a
lithium-ion battery is high, lithium-ion batteries are being
rapidly developed. Lithium-ion batteries do not use heavy metals,
such as cadmium (Cd) and mercury (Hg), and thus, are more
environmentally friendly. A lithium ion battery can be recharged at
least one thousand times, in a normal state. Accordingly, with the
development in information communication technologies, research
into secondary batteries is rapidly occurring, based on the
above-described advantages.
[0008] Generally, a lithium ion battery (hereinafter referred to as
"secondary battery"), includes a can, an electrode assembly, and a
cap assembly. The can is in a hollow structure that includes an
opening on one side. The opening of the can is sealed by the cap
assembly. In other words, the can and the cap assembly form an
external case of the secondary battery. The electrode assembly is
contained within the can, the opening of the can is sealed by the
cap assembly, electrolyte is injected in the can through an opening
in the cap, and then the opening is sealed.
[0009] The rechargeable electrode assembly includes a positive
electrode plate, a negative electrode plate, and a separator
disposed between the positive electrode plate and the negative
electrode plate. The components of the electrode assembly are wound
together. The positive electrode plate includes a positive
electrode collector made of a metal foil having an excellent
conductivity, for example, aluminum (Al) foil, and a positive
electrode active material is coated on both surfaces of the
positive electrode collector. Positive electrode non-coating
portions, where the positive electrode active material is not
coated, are formed on both ends of the positive electrode
plate.
[0010] The negative electrode plate includes a negative electrode
collector made of a conductive metal foil, for example, a copper
(Cu) or nickel (Ni) foil, and a negative electrode active material
coated on both surfaces of the negative electrode collector.
Negative electrode non-coating portions, where the negative
electrode active material is not coated, are formed on both ends of
the negative electrode plate. Electrode taps are attached to each
of the positive electrode non-coating portion and the negative
electrode non-coating portion.
[0011] As described above, a basic function of the separator is to
separate the positive electrode plate from the negative electrode
plate, and thereby prevent a short-circuit between the two plates.
It is important that the separator absorbs an electrolyte needed
for a battery reaction, and has high ion conductivity. In
particular, in the case of the lithium ion battery, there is a need
to prevent the movement of materials that obstruct the battery
reaction, and/or protect against the occurrence of abnormalities.
The separator generally includes a polyethylene-based, porous,
polymer film, such as, polypropylene, polyethylene, and the like,
in one or more layers.
[0012] However, the porous film of existing separators is formed as
a sheet or film. Accordingly, there are disadvantages that pores of
the porous film are blocked, due to generated heat, which can be
caused by an internal short-circuit, or overcharging, which cause
the sheet-typed separator to contract. When the sheet-typed
separator contracts, due to the generated heat, the positive
electrode plate contacts the negative electrode plate, where the
contraction occurs, and thereby causing the internal short-circuit.
Such a short circuit can result in a fire or an explosion.
[0013] The film-typed separator may shut-down a secondary battery,
by inhibiting the movement of lithium ions, that is, by preventing
the flow of current, by softening the polypropylene or polyethylene
resin, when the short-circuit and the heat generation occurs.
However, the film-typed separator has a fragile structure. For
example, in a nail test, which is a simulated internal
short-circuit, the temperature at the internal short-circuit
locally exceeds millions of .degree. C., and thus, the
transformation of the porous film may be accompanied by the
softening or loss of resin, which allows the nail to penetrate the
positive electrode and the negative electrode, thereby causing
abnormal overheating. Accordingly, the shut-down effect of a resin
may not completely prevent the internal short-circuit.
[0014] Specifically, as it is required to stably prevent the
internal short-circuit between the electrodes, even at a high
temperature, a separator including a ceramic layer is provided. The
ceramic layer includes a porous film which is formed by coupling
ceramic particles with a binder. The separator may be referred to
as a ceramic separator. The ceramic layer may be used alone, or
along with an existing resin separator.
[0015] The ceramic layer of the ceramic separator may be coated on
a plate of the electrode assembly. If an internal short-circuit of
the battery occurs, the ceramic layer does not contract or melt.
Also, the ceramic layer has good charging and discharging
properties, and high efficiency, due to having a high porosity.
Since the ceramic layer quickly absorbs an electrolyte, an
injection speed of the electrolyte is improved.
[0016] However, the material cost may increase upon forming of a
ceramic layer. Also, the ceramic layer is generally added to an
existing resin separator, and thus, the entire volume of a
secondary battery may increase, and the mass-to-battery capacity of
the secondary battery may be reduced.
SUMMARY OF THE INVENTION
[0017] Aspects of the present invention provide an electrode
assembly of a secondary battery that includes a ceramic layer to
improve the safety of the secondary battery. The electrode assembly
can be produced at a lower cost, and can have an increased
mass-to-battery capacity, according to the addition of the ceramic
layer. Aspects of the present invention also relate to a secondary
battery using the electrode assembly.
[0018] According to an aspect of the present invention, there is
provided an electrode assembly of a secondary battery, including: a
positive electrode plate comprising a positive electrode active
material applied to a positive electrode collector; a negative
electrode plate comprising a negative electrode active material
applied to a negative electrode collector; a separator disposed
between the positive electrode plate and the negative electrode
plate; and a ceramic layer to prevent a short-circuit between the
positive electrode plate and the negative electrode plate,
extending from a winding end of the positive electrode plate, along
between about 40% and about 90% of the length of the positive
electrode plate. The positive electrode plate, the negative
electrode plate, the ceramic layer, and the separator are wound
together.
[0019] According to some embodiments, the ceramic layer may extend
along less than 70% of the length of the positive electrode plate,
from the winding end. The winding end is located at an outer ring
of the electrode assembly.
[0020] According to some embodiments, the ceramic layer may extend
along between about 45% and about 70% of the length of the positive
electrode plate, from the winding end.
[0021] According to some embodiments, the separator may include a
polymer resin film, and the ceramic layer may be formed on at least
one surface of the separator.
[0022] According to some embodiments, the ceramic layer may be
formed on at least one surface of the negative electrode plate.
[0023] According to some embodiments, the negative electrode plate
may include a non-coating portion, where the negative electrode
active material is not applied to the negative electrode plate, and
the ceramic layer may cover the non-coating portion. The ceramic
layer may be formed on a layer of the negative electrode active
material applied to the negative electrode plate.
[0024] According to some embodiments, the ceramic layer may be
formed on at least one surface of the positive electrode plate. In
this instance, the positive electrode plate may include a
non-coating portion, where the positive electrode active material
is not applied on the positive electrode collector, and the ceramic
layer may cover the non-coating portion. Also, the ceramic layer
may be formed on a layer of the positive electrode active material
applied on the positive plate.
[0025] According to some embodiments, the negative electrode plate
may be wound in an outer location than the positive electrode
plate, and the ceramic layer may be formed on one of both surfaces
of the negative electrode plate, the one surface facing the
positive electrode plate.
[0026] According to some embodiments, the positive electrode plate
may be wound outside of the negative electrode plate, and the
ceramic layer may be formed on a surface of the negative electrode
plate, facing the positive electrode plate.
[0027] According to another aspect of the present invention, there
is provided an electrode assembly of a secondary battery including:
a positive electrode plate including a positive electrode active
material applied to a positive electrode collector; a negative
electrode plate including a negative electrode active material
applied to a negative electrode collector; and a separator disposed
between the positive electrode plate and the negative electrode
plate. The positive electrode plate, the negative electrode plate,
and the separator are wound together. The electrode assembly
comprises a ceramic layer, which is formed in a location to prevent
a short-circuit between the positive electrode plate and the
negative electrode plate. The ceramic layer is formed along between
about 40% and about 90% of the length of the negative electrode
plate, from a winding end of the negative electrode plate. The
winding end is located at an outer ring of the electrode
assembly.
[0028] According to an aspect of the present invention, there is
provided a secondary battery including: a can having an opening
formed on one side; an electrode assembly disposed in the can. The
electrode assembly comprises: a positive electrode plate including
a positive electrode active material applied to a positive
electrode collector; a negative electrode plate including a
negative electrode active material applied to a negative electrode
collector; a separator disposed between the positive electrode
plate and the negative electrode plate. The positive electrode
plate, the negative electrode plate, and the separator are wound
together. The electrode assembly further comprises a ceramic layer
formed in a location to prevent a short-circuit between the
positive electrode plate and the negative electrode plate. The
ceramic layer extends along between about 40% and about 90% of the
length of the positive electrode plate, from a winding end of the
positive electrode plate. The secondary battery further comprises a
cap assembly comprising a cap plate to seal the opening of the can,
and an electrode terminal coupled with the cap plate in an
insulated state, and electrically connected to the electrode
assembly.
[0029] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] These and/or other aspects and advantages of the invention
will become apparent and more readily appreciated from the
following description of the exemplary embodiments, taken in
conjunction with the accompanying drawings, of which:
[0031] FIG. 1 is a perspective view illustrating an electrode
assembly, according to an exemplary embodiment of the present
invention;
[0032] FIG. 2 is a top view of the electrode assembly of FIG.
1;
[0033] FIG. 3 illustrates a range over which a ceramic layer may be
formed on an electrode assembly, according to the exemplary
embodiment of FIG. 1;
[0034] FIG. 4 is a cross-sectional view illustrating a CT
photograph of a nail test of an electrode assembly, employing an
existing ceramic separator;
[0035] FIG. 5 illustrates a range of forming a ceramic layer of an
electrode assembly, according to another exemplary embodiment of
the present invention;
[0036] FIG. 6 is a perspective view illustrating an electrode
assembly, according to still another exemplary embodiment of the
present invention;
[0037] FIG. 7 is a top view of an electrode assembly, according to
the embodiment of FIG. 6;
[0038] FIG. 8 is a partial cross-sectional view illustrating an
electrode assembly, according to yet another exemplary embodiment
of the present invention;
[0039] FIG. 9 is a partial cross-sectional view illustrating an
electrode assembly, according to another exemplary embodiment of
the present invention; and
[0040] FIG. 10 is an exploded-perspective view illustrating an
embodiment of a secondary battery employing an electrode assembly,
according to each of the embodiments of FIGS. 5 and 6.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0041] Reference will now be made in detail to the exemplary
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The exemplary
embodiments are described below, in order to explain the aspects of
the present invention, by referring to the figures.
[0042] FIG. 1 is a perspective view illustrating an electrode
assembly 10, according to an exemplary embodiment of the present
invention, and FIG. 2 is a top view of the electrode assembly of
FIG. 1. FIG. 3 illustrates a formation range of a ceramic layer of
the electrode assembly 10. FIG. 4 is a cross-sectional view
illustrating a CT photograph in a nail test, of an electrode
assembly employing an existing ceramic separator.
[0043] The electrode assembly 10, according to an exemplary
embodiment of the present invention, includes a positive electrode
plate 11, a negative electrode plate 12, separators 13, 14, and 15,
a ceramic layer 16, and a pair of electrode tabs 17 and 18. The
positive electrode plate 11 includes a positive electrode collector
11a, which is made of a metal thin-film with excellent
conductivity, for example, an aluminum (Al) foil; and a positive
electrode active material 11b that is applied on one surface of the
positive electrode collector 11a.
[0044] The positive electrode active material 11b can include
chalcogenide compounds. For example, a complex metal oxide, such
as, LiCoO.sub.2, LiMnO.sub.4, LiNiO.sub.2, LiMnO.sub.2, and the
like, may be used. However, the present invention is not limited in
this regard. A region where the positive electrode active material
11b is not applied, that is, a positive electrode non-coating
portion, is formed on both ends of the positive electrode collector
11a.
[0045] The negative electrode plate 12 includes a negative
electrode collector 12a, which is made of a conductive metal
thin-film, for example, a copper (Cu) or Nickel (Ni) foil; and a
negative electrode active material 12b, which is applied on both
surfaces of the negative electrode collector 12a. The negative
electrode active material 12b can include a carbon-based material,
Si, Sn, tin, an oxide, composite tin alloys, a transition metal
oxide, a lithium metal nitride, a lithium metal oxide, and the
like. However, the present embodiment is not limited in this
regard. A region where the negative electrode active material 12b
is not applied, that is, a negative electrode non-coating portion,
is formed on both ends of the negative electrode collector 12a.
[0046] Each of the separators 13, 14, and 15 is formed of a film
including a polymer resin. The separator 14 is disposed between the
positive electrode plate 11 and the negative electrode plate 12,
and thereby prevents a short-circuit from occurring between the two
plates.
[0047] The ceramic layer 16 is included in an outer region of the
electrode assembly 10. In the present exemplary embodiment, the
ceramic layer 16 is formed on a portion of the separator 14 that is
disposed between the positive electrode plate 11 and the negative
electrode plate 12. Specifically, the ceramic layer 16 is formed on
greater than 40% of the length of the positive electrode plate 11,
from a winding end thereof, which is located at an outer ring of
the electrode assembly 10. The ceramic layer 16 may extend along
less than 90% of the length of the positive electrode plate 11, as
measured from the winding end of the positive electrode plate
11.
[0048] Referring to FIG. 3, the area at which the ceramic layer 16
is disposed on the positive electrode plate 11, of the electrode
assembly 10, is shown in FIG. 3. As shown in FIG. 3, the ceramic
layer 16 extends along about 40% of the length of the positive
electrode plate 11, from the winding end of the positive electrode
plate 11. Specifically, L1 indicates the length of the positive
electrode plate 11, and L2 indicates the length of the ceramic
layer 16. The ratio of L1 to L2 is 5:2. Accordingly, as shown in
FIG. 2, the ceramic layer 16 is located in the outer region of the
electrode assembly 10.
[0049] Line "A", shown in FIG. 3, indicates a maximum length of the
ceramic layer 16. Specifically, line A corresponds to 90% of the
length of the positive electrode plate 11, from the winding end of
the positive electrode plate 11. Line B indicates 70% of the length
of the positive electrode plate 11, from the winding end of the
positive electrode plate 11. The ceramic layer 16 may extend from
the winding end of the positive electrode plate 11, to at least
line B, and to at most line A.
[0050] The 40% length from the winding end of the positive
electrode plate 11, based on the entire length of the positive
electrode plate 11, indicates a minimum, or near formation range of
the ceramic layer 16, which does not result in firing or explosion
of the electrode assembly 10, when the electrode assembly 10 is
penetrated. According to some embodiments, the ceramic layer 16 is
formed to extend along about 40% to about 70% of the length of the
positive electrode plate 11, from the winding end of the positive
electrode plate 11. When the ceramic layer 16 is formed to less
than 70% of the length of the positive electrode plate 11, the
volume of electrode assembly 10 may be reduced.
[0051] According to some embodiments, the ceramic layer 16 is
formed to extend along about 45% to about 70% of the length of the
positive electrode plate 11, from the winding end of the positive
electrode plate 11. This is because the ceramic layer 16 may be
more protected from firing or explosion of the electrode assembly
10, when the ceramic layer 16 is greater than about 45% of the
length of the positive electrode plate 11.
[0052] The ceramic layer 16 can be a porous film that includes
secondary particles of a ceramic material and a binder. The ceramic
layer 16 is formed by sintering, or melting, the secondary
particles, and the re-crystallizing a portion of the same, in the
binder. The secondary particles may be oriented in a radial shape
(in the shape of grapes), or a sedimentary shape.
[0053] The ceramic material may include at least one of SiO.sub.2,
Al.sub.2O.sub.3, ZrO.sub.2, and TiO.sub.2. For example, ceramic
material may be at least one of hydroxide, alkoxide, ketonese, and
an insulating nitride, of Si, Al, Zr, and/or Ti. The binder may
include polymer resin, and may include any one of a polymer of
acrylate, or methacrylate, or a copolymer thereof.
[0054] The ceramic layer 16 may be formed by dipping, spraying, or
printing, the positive electrode plate 11, the negative electrode
plate 12, or the film separator 14 with a mixed solution of the
binder, a solvent, and the secondary particles of the ceramic
material. The printing generally involves using a gravure
roller.
[0055] The electrode tabs 17 and 18 are attached to the positive
electrode non-coating portion of the positive electrode plate 11,
and the negative electrode non-coating portion of the negative
electrode plate 12, respectively. The ceramic layer 16 is formed in
a minimum region, where the safety of the secondary battery can be
secured. As a result, it is possible to reduce the manufacturing
costs of the electrode assembly 10 and the secondary battery. Also,
it is possible to secure against an internal short-circuit of the
secondary battery.
[0056] Referring to FIG. 4, the CT photograph shows the nail test
of the electrode assembly employing an existing ceramic separator.
As shown in FIG. 4, it can be seen that heat-generation, or
heat-absorption, and loss of the active material, generally occur
in an outer portion of the electrode assembly.
[0057] The penetration was performed in the direction of the arrow
of FIG. 4. A penetrated portion of the electrode assembly, and a
portion damaged by heat, is shown in black. The damaged portion is
concentrated where the initial penetration of the electrode
assembly occurred. Other portions that were penetrated later were
not damaged by heat. This shows that the ceramic separator
functions to inhibit a short-circuit caused by the heat generated
during the initial penetration of the electrode assembly.
Therefore, according to aspects of the present invention, although
the ceramic separator is limited to the outer region of the
electrode assembly, it is possible to prevent a short-circuit from
occurring, due to the heat from the initial penetration of the
electrode assembly, and thereby insure the safety of a secondary
battery.
[0058] Referring to Table 1 below, when the ceramic layer 16 is not
formed on the electrode assembly 10, or when the ceramic layer 16
is formed on less than 40% of the length from the winding end,
based on the entire length of the positive electrode plate 11, all
tested electrode assemblies in the nail test exploded, and the
inner temperature of the batteries was 200.degree. C., or more.
[0059] However, when the ceramic layer 16 was formed on more than
about 40%, and less than around 50%, of the length of the positive
electrode plate 11, from the winding end, the electrode assemblies
did not explode in the nail tests, and the temperatures of the
batteries was less than 100.degree. C.
TABLE-US-00001 TABLE 1 Formation range of ceramic layer (%) Nail
test results Average temperature (.degree. C.) 0 5 NG 262.3 10 5 NG
274.2 30 5 NG 263.4 40 1OK 4 NG 171.9 50 5 OK 80.0 60 5 OK 81.1 70
5 OK 81.3 90 5 OK 75.0 100 5 OK 74.9
[0060] FIG. 5 illustrates a ceramic layer 16' formed to extend from
a winding end, across 60% of the length of a positive electrode
plate 11. Specifically, the ratio of L1 to L2 is 5:3, where L1 is
the length of the positive electrode plate 11 and L2 is the length
of the ceramic layer 16'. Lines A and B are the same as lines A and
B of FIG. 3.
[0061] FIG. 6 is a perspective view illustrating an electrode
assembly 110, according to still another exemplary embodiment of
the present invention, and FIG. 7 is a top view of the electrode
assembly 110 of FIG. 6. The electrode assembly 110 includes a
positive electrode plate 111, a negative electrode late 112,
separators 113, 114, and 115, a ceramic layer 116, and a pair of
electrode tabs 117 and 118.
[0062] As shown in FIGS. 5 and 6, the ceramic layer 116 is formed
in an outer region of the electrode assembly 110, which is
rectangular. In other words, the embodiment of FIGS. 1 through 3
disposes the ceramic layer 16 in the outer region of the
cylindrical electrode assembly 10, and the ceramic layer 116 is
disposed in the outer regions of the rectangular electrode assembly
110. However, other basic components are the same. Accordingly,
similar aspects of the present embodiment will be briefly
described.
[0063] Specifically, the electrode assembly 110 includes: the
positive electrode plate 111 that includes a positive electrode
active material 111b applied to a positive electrode collector
111a; the negative electrode plate 112 that includes a negative
electrode active material 112b applied to a negative electrode
collector 112a; a pair of electrode tabs 117 and 118 attached to
the positive electrode plate 111 and the negative electrode plate
112, respectively; film-type separators 113, 114, and 115; and the
ceramic layer 116. The positive electrode plate 111 and the
negative electrode plate 112 have the same general configuration as
in the cylindrical electrode assembly 10, according to the
embodiment of FIGS. 1 through 3. The separator 114 formed on one
surface of the ceramic layer 116 is disposed between the positive
electrode plate 111 and the negative electrode plate 112.
[0064] FIG. 8 is a partial cross-sectional view illustrating an
electrode assembly, according to yet another exemplary embodiment
of the present invention. As shown in FIG. 8, in the electrode
assembly, a ceramic layer 316 is formed on one surface of a
negative electrode plate 312. In this instance, the ceramic layer
316 may be formed on a section where a negative electrode active
material 312b of the negative electrode plate 312 is applied, and
extends to section where the negative electrode active material
312b is not applied, that is, a non-coating portion.
[0065] FIG. 9 is a partial cross-sectional view illustrating an
electrode assembly, according to another exemplary embodiment of
the present invention. As shown in FIG. 9, in the electrode
assembly, a ceramic layer 416 is formed on at least one surface of
a positive electrode plate 411. In this instance, the ceramic layer
416 may be formed on a section where a positive electrode active
material 411b of the positive electrode plate 411 is applied, and
extends to another section of a positive electrode collector 411a,
where the positive electrode active material 411b is not applied,
that is, a non-coating portion.
[0066] The embodiments of FIGS. 1 through 9 described the length of
the ceramic layers 16, 116, 316, and 416, based on the entire
length of the positive electrode plates 11, 111, 311, and 411,
respectively. However, in the electrode assembly, the length of a
positive electrode plate is generally the same as, or almost same
as, the length of a corresponding negative electrode plate.
Accordingly, applying the configuration of the ceramic layers 16,
116, 316, and 416, according to the embodiments of FIGS. 1 through
9, based on the entire length of the negative electrode plates 12,
112, 312, and 412, will result in the same operations.
[0067] FIG. 10 is an exploded perspective view illustrating an
exemplary embodiment of a secondary battery employing an electrode
assembly 110, according to the embodiments of FIGS. 5 and 6. The
secondary battery includes an electrode assembly 110, a can 20, and
a cap assembly 30. Since the electrode assembly 10 has been
described above, with reference to FIGS. 5 and 6, a detailed
description thereof is omitted.
[0068] The can 20 is formed in a shape of a rectangular prism, or a
nearly rectangular prism. The can 20 includes an opening on one
side and the electrode assembly 10 is inserted into the can 20, via
the opening. The can 20 may be formed of any one of Al, a Ni plated
aluminum, Fe, SUS, Cu, a Cu alloy, or equivalents thereof.
[0069] The cap assembly 30 includes a cap plate 31, an electrode
terminal 32, an insulation gasket 33, an insulation plate 34, a
terminal plate 35, a safety vent 36, and a stopper 37. The cap
plate 31 is coupled with the opening of the can 20, and thereby
seals the can 20. The cap plate 31 is welded on the opening of the
can 20. A stepped edge 22 is formed along the edge of the opening
of the can 20. The cap plate 31 may be coupled with the opening, by
being welded to the stepped edge 20. The cap plate 31 includes a
terminal hole 31a, an electrolyte injection hole 31b, and the
safety vent 36.
[0070] The electrode terminal 32 is inserted into the cap plate 31,
via the terminal hole 31a, from the top of the cap plate 31. The
electrode terminal 32 includes the insulation gasket 33, which is
disposed around the electrode terminal 32, and is then inserted via
the terminal hole 31a, to insulate the electrode terminal 32 from
the cap plate 31.
[0071] The insulation plate 34 and the terminal plate 35 are
sequentially provided below the cap plate 31. The insulation plate
34 and the terminal plate 35 are coupled with the electrode
terminal 32, which is inserted via the terminal hole 31a. The
terminal plate 35 is electrically connected to one pole of the
electrode assembly 110. Generally, the negative pole of the
electrode assembly 110 is electrically connected to the electrode
terminal 32. The insulation plate 34 prevents an electrical
short-circuit between the cap plate 31 and the terminal plate
35.
[0072] Although a few exemplary embodiments of the present
invention have been shown and described, it would be appreciated by
those skilled in the art that changes may be made in these
exemplary embodiments, without departing from the principles and
spirit of the invention, the scope of which is defined in the
claims and their equivalents.
* * * * *